Baseline N-terminal Pro-brain Natriuretic Peptide Research Articles

Reperfusion before percutaneous coronary intervention in ST-elevation myocardial infarction patients is associated with lower N-terminal pro-brain natriuretic peptide levels during follow-up, irrespective of pre-treatment with full-dose fibrinolysis

N-terminal pro-brain natriuretic peptide (NT-proBNP) levels predict outcomes in ST-elevation myocardial infarction patients treated with fibrinolysis or primary percutaneous coronary intervention (PCI). However, its role in facilitated PCI has not yet been assessed; it may be a tool to evaluate the lower event rates with primary PCI in ASSENT-4. In ASSENT-4, 1667 patients were randomized to tenecteplase (TNK) followed by PCI or primary PCI alone. Baseline, discharge/Day 7, and 90-day NT-proBNP levels were available for 1008, 971, and 813 patients. Increasing quartiles of baseline NT-proBNP levels were associated with a higher risk of the combined endpoint of death, heart failure, and shock at 90 days and 1-year mortality (P < 0.001). Events were more common with TNK + PCI, regardless of baseline NT-proBNP quartile. When analysing baseline NT-proBNP as a continuous variable, no treatment interaction was observed for the primary endpoint (P = 0.17) or 1-year mortality (P = 0.08). Overall, NT-proBNP levels at Day 7 or 90 were not different between the two treatments. In patients with TIMI 2-3 flow before PCI, NT-proBNP at Day 90 was lower in PCI-only patients (P = 0.01), although no interaction was observed (P = 0.14). In TNK-pre-treated patients without reperfusion (TIMI 0-1) after PCI, NT-proBNP levels at Day 7 or 90 were not significantly higher than in PCI patients. Baseline NT-proBNP predicts outcome at 90 days and 1 year in patients undergoing PCI with or without facilitation with TNK. A higher rate of reperfusion in lytic-pre-treated patients did not result in lower NT-proBNP during follow-up. Thus, baseline and subsequent NT-proBNP levels do not explain the lower mortality rate with PCI alone seen in this trial.

Variability of N-Terminal Probrain Natriuretic Peptide in Stable Chronic Heart Failure and Its Relation to Changes in Clinical Variables

We investigated the variability of N-terminal probrain natriuretic peptide (NT-proBNP) and its relation to known confounding variables in patients with stable chronic heart failure who were on a stable optimized medication regimen. At 4 sampling intervals (14-day, 1-month, 2-month, and 3-month) the results for NT-proBNP measurements and several clinical variables were measured in samples from 41 patients with chronic systolic dysfunction who met 21 prespecified criteria for stability. Mean within-person NT-proBNP variabilities expressed as percentage CV were 17.6%, 18.9%, 15.5%, and 16.2% at 14-day, 1-month, 2-month, and 3-month follow-up, respectively, and the corresponding reference change values were 34.6%, 52.5%, 43.1%, and 45.0%, respectively. Within-person variability of NT-proBNP was not found to be associated with renal function, weight, or waist circumference. Likewise, age, sex, baseline NT-proBNP, New York Heart Association functional class, and ejection fraction did not influence variability of NT-proBNP. The index of individuality ranged from 0.07-0.15 depending on the time interval between test results. Although other reported studies have revealed variations in the range of 80%, in this prespecified stable heart-failure population variation of NT-proBNP at 14-day, 1-month, 2-month, and 3-month follow-up was lower and was not related to renal function or weight. In view of the low index of individuality we observed, within-person variation is quite low compared to between-person variation. Consideration of these facts is important for the interpretation of clinical trials and the use of NT-proBNP in monitoring patients with heart failure.

Left ventricular remodelling in patients with moderate systolic dysfunction after myocardial infarction: favourable effects of exercise training and predictive role of N-terminal pro-brain natriuretic peptide

To investigate the effects of exercise training (ET) on left ventricular (LV) volumes, cardiopulmonary functional capacity and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in postinfarction patients with moderate LV dysfunction. Sixty-one postinfarction patients were randomized into two groups: group T [n=30, LV ejection fraction (EF) 41.6+/-11.3%, mean+/-SD] entered a 6-month ET programme, whereas group C (n=31, EF 42.0+/-7.6%, P=NS) did not. NT-proBNP assay, Doppler-echocardiography and cardiopulmonary exercise test were performed upon enrolment and at sixth months. At sixth months, trained patients showed an improvement in workload (+26%, P<0.001), Vo2peak (+31%, P<0.001), LV end-diastolic volume index (LVEDVI; -9%, P<0.001), a reduction in NT-proBNP (-71%, P<0.001) and a significant correlation between changes in NT-proBNP and in LVEDVI (r=0.858, P<0.001). Baseline NT-proBNP correlated with changes in LVEDVI in both trained (r=0.673, P<0.001) and untrained (r=0.623, P<0.001) patients. Group C showed unfavourable LVEDVI dilation (+8%, P<0.001; T vs. C group, P<0.001) and a smaller reduction in NT-proBNP (-40%, P<0.001; T vs. C group, P<0.001). Six month ET induced a favourable LV remodelling and a marked fall in NT-proBNP that could predict LV remodelling in postinfarction patients with moderate LV dysfunction.

High N‐terminal pro–brain natriuretic peptide levels and low diffusing capacity for carbon monoxide as independent predictors of the occurrence of precapillary pulmonary arterial hypertension in patients with systemic sclerosis

To evaluate predictors of pulmonary arterial hypertension (PAH) in a prospective cohort of patients with systemic sclerosis (SSc). Routine clinical assessments as well as measurements of the diffusing capacity for carbon monoxide/alveolar volume (DLCO/VA) ratio and N-terminal pro-brain natriuretic peptide (NT-proBNP) level were performed in a prospective cohort of 101 SSc patients who did not have PAH or severe comorbidities. After a planned 36-month followup, we evaluated the predictive value of these parameters for the development of precapillary PAH, as demonstrated by cardiac catheterization, disease progression, and death. Criteria for cardiac catheterization were a systolic pulmonary artery pressure (PAP) of >40 mm Hg on echocardiography, a DLCO value of <50% without pulmonary fibrosis, and unexplained dyspnea. Eight patients developed PAH, 29 had disease progression, and 10 died during a median followup of 29 months. Kaplan-Meier analysis identified the following baseline parameters as being predictors of PAH: DLCO/VA ratio <70% or <60% (P<0.01 for each comparison), elevated plasma NT-proBNP level (>97th percentile of normal; P = 0.005), echocardiographically estimated systolic PAP >40 mm Hg (P=0.08), and erythrocyte sedimentation rate >28 mm/hour (P=0.015). In multivariate analyses, an elevated baseline NT-proBNP level (hazard ratio [HR] 9.97 [95% confidence interval (95% CI) 1.69-62.42]) and a DLCO/VA ratio <60% (HR 36.66 [95% CI 3.45-387.6]) were predictors of the occurrence of PAH during followup. An increased NT-proBNP level together with a decreased DLCO/VA ratio of <70% was highly predictive of the occurrence of PAH during followup (HR 47.20 [95% CI 4.90-450.33]). This prospective study identified a decreased DLCO/VA ratio and an increased NT-proBNP as predictors of PAH in SSc. Use of these markers should result in improved PAH risk stratification and allow earlier initiation of therapy.

Effect of pioglitazone on heart function and N-terminal pro-brain natriuretic peptide levels of patients with type 2 diabetes

We assessed the effect of the addition of pioglitazone on metabolic control and heart function of patients with type 2 diabetes already receiving sulfonylurea plus metformin. Forty-four patients were given 30 mg of pioglitazone for 3 months. Physical examination, laboratory tests including N-terminal pro-brain natriuretic peptide (NT-proBNP), and echocardiography, were performed at baseline and at study completion. Target HbA(1c) levels were achieved by 44.2% of the patients. Pioglitazone ameliorated lipid profile and lowered liver enzymes and C-reactive protein. Significant increases in NT-proBNP by 39% (P < 0.005) were noticed, but echocardiographic parameters were not altered, even in high-risk subgroups (patients older than 60 years, with diabetes for more than 10 years, with hypertension, with elevated baseline NT-proBNP levels, with left ventricular hypertrophy). In patients with a greater than 60% increase in NT-proBNP levels, a significant increase in left ventricular ejection fraction (P < 0.05) and in fractional shortening (P < 0.05) was found. None of the patients developed edema or signs or symptoms of heart failure. Triple oral combination antidiabetic treatment is an effective therapeutic strategy and weight gain does not abrogate its beneficial actions. Pioglitazone does not affect heart function and even though it increases NT-proBNP, this appears to represent a reaction to volume overload.

N-terminal pro–brain natriuretic peptide for additional risk stratification in patients with non–ST-elevation acute coronary syndrome and an elevated troponin T: An Invasive versus Conservative Treatment in Unstable coronary Syndromes (ICTUS) substudy

New evidence has emerged that the assessment of multiple biomarkers such as cardiac troponin T (cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients with non-ST-elevation acute coronary syndrome (nSTE-ACS) provides unique prognostic information. The purpose of this study was to assess the association between baseline NT-proBNP levels and outcome in patients who have nSTE-ACS with an elevated cTnT and to determine whether patients with elevated NT-proBNP levels benefit from an early invasive treatment strategy. Baseline samples for NT-proBNP measurements were available in 1141 patients who have nSTE-ACS with an elevated cTnT randomized to an early or a selective invasive strategy. Patients were followed-up for the occurrence of death, myocardial infarction (MI), and rehospitalization for angina. We showed that increased levels of NT-proBNP were associated with several indicators of risk and severe coronary artery disease. Mortality by 1 year was 7.3% in the highest quartile (> or = 1170 ng/L for men, > or = 2150 ng/L for women) compared with 1.1% of patients in the lower 3 quartiles (P < .0001). N-terminal pro-brain natriuretic peptide (highest quartile vs lower 3 quartiles) was a strong independent predictor of mortality (hazard ratio 5.0, 95% CI 2.1-11.6, P = .0002). However, NT-proBNP levels were not associated with the incidence of recurrent MI by 1 year. Furthermore, we could not demonstrate a benefit of an early invasive strategy compared with a selective invasive strategy in patients with an elevated NT-proBNP level. We confirmed that NT-proBNP is a strong independent predictor of mortality by 1 year but not of recurrent MI in patients who have nSTE-ACS with an elevated cTnT. We could not demonstrate a benefit of an early invasive strategy compared with a selective invasive strategy.

Epidemiology and New Predictors of Atrial Fibrillation After Coronary Surgery

Postoperative atrial fibrillation (PAF) is a frequent complication of coronary artery bypass grafting (CABG). Our aims were to study its epidemiology and to identify predictors in everyday clinical practice, while taking into account statin use, extracorporeal circulation, and new biomarkers of inflammation and ventricular stress. The study included 102 consecutive patients (65 [9] years, 72% male) who were undergoing CABG. Blood samples were taken the day before surgery to determine baseline levels of C-reactive protein (CRP) and N-terminal probrain natriuretic peptide (NT-proBNP). Details of baseline clinical characteristics, preoperative treatment and surgery were recorded. The end-point was PAF at 30 days. The incidence of PAF was 23% (n=23; 3.2 [2.9] days, range 1-15 days). Its appearance was associated with a longer stay in the intensive care unit (+ 1 day; P=.019), but not with an increased total hospital stay (P=.213). Among patients with PAF, 4.3% had an embolism and 8.6% remained in atrial fibrillation at discharge. Moreover, PAF was associated with a longer duration of ischemia (28.5 [22.3] vs 18.0 [27.9]; P=.045) and a lower statin pretreatment rate (39% vs 66%; P=.022). Multivariate analysis showed that the only factor associated with a higher risk of PAF was the absence of statin pretreatment (odds ratio = 4.31, 95% confidence interval 1.33-13.88; P=.015). There was no association between either extracorporeal circulation or the baseline CRP or NT-proBNP level and an increased risk of PAF. In everyday clinical practice, PAF is a frequent complication. Statin pretreatment could have a protective effect against its appearance.

Use of N-terminal pro-brain natriuretic peptide to detect acute cardiac dysfunction during weaning failure in difficult-to-wean patients with chronic obstructive pulmonary disease*

To evaluate the utility of serial measurements of plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) to detect acute cardiac dysfunction during weaning failure in difficult to wean patients with chronic obstructive pulmonary disease. Prospective observational cohort study. A 14-bed general intensive care unit in a university hospital. Nineteen patients mechanically ventilated for chronic obstructive pulmonary disease exacerbation who were difficult to wean. None. Cardiac and hemodynamic variables, arterial and central venous blood gas, breathing pattern, respiratory mechanics, indexes of oxygen cost of breathing, and plasma levels of NT-proBNP were measured and analyzed immediately before (baseline) and at the end of a spontaneous breathing trial. Eight of 19 patients (42%) were identified with acute cardiac dysfunction at the end of the weaning trial. Baseline NT-proBNP levels were significantly higher (median 5000, interquartile range 4218 pg/mL) in these patients than in patients without evidence of acute cardiac dysfunction (median 1705, interquartile range 3491 pg/mL). Plasma levels of NT-proBNP increased significantly at the end of the spontaneous breathing trial only in patients with acute cardiac dysfunction (median 12,733, interquartile range 16,456 pg/mL, p < .05). The elevation in NT-proBNP at the end of the weaning trial had a good diagnostic performance in detecting acute cardiac dysfunction, as estimated by area under the receiver operating characteristic curve analysis (area under the curve 0.909, se 0.077, 95% confidence interval 0.69-0.98; p < .0001, cutoff = 184.7 pg/mL). Serial measurements of NT-proBNP plasma levels provided a noninvasive manner to detect acute cardiac dysfunction during an unsuccessful weaning trial in difficult to wean patients with chronic obstructive pulmonary disease. The utility of this test as a complement of the standard clinical monitoring of the weaning trial deserves further investigation.

N‐terminal pro‐brain natriuretic peptide for detection of cardiovascular stress in patients with obstructive sleep apnea syndrome

Patients with obstructive sleep apnea syndrome (OSAS) have an elevated incidence of cardiovascular events that may be related to an increased ventricular load and hypoxemia caused by apneas and hypopneas. N-terminal pro-brain natriuretic peptide (NTproBNP) appears to be an excellent marker of myocardial stretch and could serve as an indicator of subclinical cardiac stress, thereby identifying a patient population at risk for cardiac effects from OSAS. Adult patients presenting with suspected OSAS and scheduled for nocturnal polysomnography were recruited. Patients with heart or renal failure or severe lung disease were excluded. NTproBNP was measured the evening before and the morning after sleep. Blood pressure (BP) was monitored intermittently throughout the night. Fifteen male and 15 female subjects with a mean +/- SD body mass index of 38.2 +/- 9.8 were studied. Mean Apnea-Hypopnea Index (AHI) was 38.4 +/- 26, with 17 subjects having severe OSAS (AHI > 30). No subject had a significant rise in BP. NTproBNP values overnight decreased in 19 patients and rose in 11 (mean change 3.8 +/- 33 pg mL(-1)), but only one patient had an abnormal morning value. Three patients had an abnormal NTproBNP value prior to sleep, but their levels decreased with sleep. No correlations were detected between the evening baseline or postsleep NTproBNP levels and OSAS. Monitoring pre- and postsleep NTproBNP levels revealed no association with the occurrence or degree of OSAS, making it unlikely that NTproBNP could serve as a marker of cardiac stress in OSAS patients with stable BP and without overt heart failure.

In Reply: The Role of NT-proBNP as a Prognostic Marker in Pulmonary Hypertension

We thank very much Dr. Souza et al for their interest in our article (May 2006) 1 Fijalkowska A Kurzyna M Torbicki A et al. Serum N-terminal brain natriuretic peptide as a prognostic parameter in patients with pulmonary hypertension. Chest. 2006; 129: 1313-1321 Abstract Full Text Full Text PDF PubMed Scopus (331) Google Scholar on the potential clinical role of N-terminal-pro-brain natriuretic peptide (NT-proBNP) estimation in patients with pulmonary arterial hypertension (PAH). We also agree with their concerns regarding the universal validity of the prognostic cutoff values that were reported in our article. Clearly, with a study group of slightly > 50 patients we would not impose or recommend such values for universal prognostic use. Furthermore, we do not believe that even the most sophisticated statistical analysis could extract more objective truth from such a database. On the other hand, by looking at the receiving operating characteristic analysis and trying to identify prognostic thresholds we wanted to avoid the common practice of reporting the prognostic significance of median values. While highly dependent on the initial characteristics of the study group of the index trial, such median values later often become surprisingly “magic numbers” and are extrapolated to other populations with even less evidence. This was the case both for a 6-min walk test distance of 332 m or an NT-proBNP concentration of 150 pg/L as a result of the reports of Nagaya et al 2 Nagaya N Nishikimi T Uematsu M et al. Plasma brain natriuretic peptide as a prognostic indicator in patients with primary pulmonary hypertension. Circulation. 2000; 102: 865-870 Crossref PubMed Scopus (713) Google Scholar and Miyamoto et al. 3 Miyamoto S Nagaya N Satoh T et al. Clinical correlates and prognostic significance of six-minute walk test in patients with primary pulmonary hypertension: comparison with cardiopulmonary exercise testing. Am J Respir Crit Care Med. 2000; 161: 487-492 Crossref PubMed Scopus (957) Google Scholar Therefore, rather than defending our 1,400 and 3,400 pg/L thresholds, even though they were derived from a receiving operating characteristic analysis, we would reply by issuing a call for pulling together data on PAH patients whose baseline clinical characteristics and NT-proBNP concentrations were tested with a method similar to the one used in our study. This may be true, for instance, for the study population of a trial recently published by Souza et al. 4 Souza R Bogossian HB Humbert M et al. N-terminal-pro-brain natriuretic peptide as a haemodynamic marker in idiopathic pulmonary arterial hypertension. Eur Respir J. 2005; 25: 509-513 Crossref PubMed Scopus (50) Google Scholar We have recently witnessed a great step forward in the understanding of the efficacy of the new drugs developed for the treatment of PAH thanks to global collaboration between expert centers. It is time to try to start building networks of collaboration to learn more about prognostic indexes and clinical end points. We would be available for this type of collaboration. The Role of NT-proBNP as a Prognostic Marker in Pulmonary HypertensionCHESTVol. 130Issue 5PreviewIn an article recently published in CHEST (May 2006), Fijalkowska et al1 provided important information on the value of N-terminal pro-type B natriuretic peptide (NT-proBNP) as a prognostic marker in patients with pulmonary hypertension (PH). There is growing interest in the role of natriuretic peptides in understanding the natural history of PH.2,3 The authors demonstrated that NT-proBNP is correlated with echocardiographic variables of right ventricular function and confirmed previous findings about the correlation of NT-proBNP with invasive hemodynamic variables. Full-Text PDF

Effect of folate supplementation on N-terminal pro-brain natriuretic peptide

Background Increased plasma homocysteine (HCY) has been suggested as a novel risk factor for chronic heart failure (CHF). This study investigated the effect of a HCY lowering therapy by folic acid (FA) supplementation on N-terminal pro-brain natriuretic peptide (NT-proBNP) in healthy subjects. Methods We treated 61 healthy individuals (median age [25th–75th percentile]: 57 [53–69] years with placebo, 0.4, 1.0 or 5.0 mg FA daily for 2 months. Fasting blood samples were taken after 0, 4 and 8 weeks. Serum HCY, folate, vitamin B 12 and NT-proBNP were studied. Results Baseline HCY, folate and NT-proBNP levels were 13.6 (10.0–16.4) μmol/L, 5.0 (3.8–6.4) μg/L and 40.4 (21.8–67.3) ng/L, respectively. Serum folate increased during supplementation (4 weeks of placebo, 0.4, 1.0, 5.0 mg of FA: − 9%, + 131%, + 150%, + 314%; 8 weeks: − 72%, + 152%, + 185%, + 62%) and HCY decreased (4 weeks: + 2%, − 12%, − 20%, − 15%; 8 weeks: − 2%, − 9%, − 17%, − 15%) in the treatment groups. NT-proBNP did not change within groups. Pooling FA treated subjects, individuals with a baseline NT-proBNP above the median of 40 ng/L exhibited a 20% decrease of NT-proBNP (significant on a 10% level) while HCY decreased by 15%. Conclusion FA supplementation with doses between 0.4 and 5 mg does not affect NT-proBNP in healthy subjects with an NT-proBNP concentration < 40 ng/L, but possibly lowers NT-proBNP in individuals with NT-proBNP levels > 40 ng/L.

The prognostic use of right heart catheterization data in patients with advanced heart failure: How relevant are invasive procedures in the risk stratification of advanced heart failure in the era of neurohormones?

Background Right heart catheterization long has been a routine investigation in advanced heart failure, and its measurements have been linked variably to prognosis. However, in the modern era, newer potential markers of prognosis are coming to light. This study reconsiders the use of right heart catheterization data and compares their use to that of N-terminal pro-brain natriuretic peptide (NT-proBNP), a neurohormone linked with prognosis in chronic heart failure. Methods We assessed prospectively the prognostic potential of baseline right heart catheterization data in 97 consecutive patients with advanced heart failure referred to the Scottish Cardiopulmonary Transplant Unit for consideration of cardiac transplantation. Patients underwent baseline routine investigation, including right heart catheterization and blood draws for NT-proBNP analysis. Patients were observed for a median of 370 days. Results The primary end-point of all-cause mortality was reached in 17 patients (17.5%), and the secondary end-point of all-cause mortality or urgent cardiac transplantation was reached in 21 (21.6%) patients. Univariate predictors of all-cause mortality included pulmonary artery systolic pressure (PASP), pulmonary artery wedge pressure (PAWP), and NT-proBNP concentration greater than their median values. Univariate predictors of the secondary end-point included right atrial pressure, PASP, PAWP, and NT-proBNP concentration greater than their median values, and left ventricular ejection fraction, cardiac output, and cardiac index less than their median values. In multivariate analyses, however, only NT-proBNP concentration remained an independent predictor of all-cause mortality. Both NT-proBNP concentration and PAWP were independent predictors of all-cause mortality and of the need for urgent cardiac transplantation. Conclusion Baseline data from routine right heart catheterization are of limited prognostic use in advanced heart failure. A baseline NT-proBNP concentration is a superior, non-invasive method of risk stratification in this era of measuring neurohormones.

Assessment of the stability of N-terminal pro-brain natriuretic peptide in vitro: implications for assessment of left ventricular dysfunction

Plasma concentrations of N-terminal pro-brain natriuretic peptide (NT-proBNP) are raised in patients with left ventricular dysfunction. Measurement of this peptide has a potential diagnostic role in the identification and assessment of patients with heart failure. The stability of this peptide over time periods and conditions pertaining to routine clinical practice has not been reported previously. Blood samples were obtained from 15 subjects. One aliquot was processed immediately, and the remaining portions of the blood samples were stored for 24 h or 48 h at room temperature or on ice prior to processing. Plasma concentrations of NT-proBNP were measured with a novel immunoluminometric assay developed within our laboratory. Mean plasma concentrations of NT-proBNP were not significantly different whether blood samples were centrifuged immediately and stored at -70 degrees C or kept at room temperature or on ice for 24 h or 48 h. The mean percentage differences from baseline (reference standard) were +5.2% (95% confidence interval +18.2 to -7.8%) and +0.8% (+15.2 to -13.7%) after storage for 24 h at room temperature or on ice respectively, and +8.9% (+24.2 to -6. 5%) and +3.2% (+15.1 to -0.9%) for storage for 48 h at room temperature or on ice respectively. Pearson correlation coefficients for baseline NT-proBNP concentrations compared with levels at 48 h at room temperature or on ice were r=0.89 and r=0.83 respectively (both P<0.0001). Thus NT-proBNP extracted from plasma samples treated with EDTA and aprotinin is stable under conditions relevant to clinical practice.

Assessment of the stability of N-terminal pro-brain natriuretic peptide in vitro: implications for assessment of left ventricular dysfunction

Plasma concentrations of N-terminal pro-brain natriuretic peptide (NT-proBNP) are raised in patients with left ventricular dysfunction. Measurement of this peptide has a potential diagnostic role in the identification and assessment of patients with heart failure. The stability of this peptide over time periods and conditions pertaining to routine clinical practice has not been reported previously. Blood samples were obtained from 15 subjects. One aliquot was processed immediately, and the remaining portions of the blood samples were stored for 24 h or 48 h at room temperature or on ice prior to processing. Plasma concentrations of NT-proBNP were measured with a novel immunoluminometric assay developed within our laboratory. Mean plasma concentrations of NT-proBNP were not significantly different whether blood samples were centrifuged immediately and stored at -70 degrees C or kept at room temperature or on ice for 24 h or 48 h. The mean percentage differences from baseline (reference standard) were +5.2% (95% confidence interval +18.2 to -7.8%) and +0.8% (+15.2 to -13.7%) after storage for 24 h at room temperature or on ice respectively, and +8.9% (+24.2 to -6. 5%) and +3.2% (+15.1 to -0.9%) for storage for 48 h at room temperature or on ice respectively. Pearson correlation coefficients for baseline NT-proBNP concentrations compared with levels at 48 h at room temperature or on ice were r=0.89 and r=0.83 respectively (both P<0.0001). Thus NT-proBNP extracted from plasma samples treated with EDTA and aprotinin is stable under conditions relevant to clinical practice.